\section{Related Work}

%Other distributed hash systems include 
There has been widespread interest in peer-to-peer and wide-area networks in the past 10 years. 
To briefly mention a few, the Gnutella and Freenet networks\cite{Clarke:2000p2008, Berkes:2003p2010} are both popular examples.

Closer to Ringer, Kosha\cite{Butt:2006p2434}, extends the basic client-server model of NFS with peer-to-peer data transfer. 
Kosha uses NFS to provide hierarchical file organization, directory listings and file permissions, very much like the MDS concept in Ringer. 
Kosha peers transfer data directly between each other, again in a similar manner to Ringer.
A key difference is that Ringer supports a de-centralized MDS network, while Kosha relies on a single NFS server to handle the metadata requests of all its clients.
Also, while Ringer has an emphasis on wide-area search, Kosha is targeted at providing local area performance. 

Another system similar to Ringer is Anglano and Ferrino's work with N3FS.
In \cite{Anglano:2004p1917}, they evaluate using the Chord \cite{Stoica:2001p1759} distributed hash table like the MDS network in Ringer to provide metadata storage and lookup.
The difference again with Ringer is its emphasis on search.

